A long term evolution (Long Term Evolution, LTE) system is a next-generation wireless communication standard being formulated by the 3rd generation partnership project (The 3rd Generation Partnership Project, 3GPP). It has advantages such as high spectrum utilization and transmission speed, and low transmission delay. The terminal of an LTE system implements uplink transmission synchronization with a base station by using a timing advance (Timing Advance, TA), and maintains uplink synchronization by using a time alignment timer (Time Alignment Timer, TAT). With the introduction of a TA, uplink transmission of all terminals can be accomplished at the time expected by the base station, thereby avoiding collision between terminals during the uplink transmission and implementing time division multiplexing.
To provide a higher data rate, the base station may configure, for the terminal, one or more secondary cells (Secondary Cells, SCells) to assist a primary cell (Primary Cell, PCell) in data transmission. The primary cell and secondary cells correspond to an uplink carrier each, where transmission over different uplink carriers may need to use different TAs. The TA corresponding to a primary cell is known as a primary TA, and the TAT corresponding to a primary cell is known as a primary TAT; the TA corresponding to a secondary cell is known as a secondary TA, and the TAT corresponding to a secondary cell is known as a secondary TAT.
In the prior art, after a secondary cell is configured, if the secondary cell does not use an existing TA of a primary cell, a terminal obtains a secondary TA of the secondary cell by initiating random access in the secondary cell. This may increase signaling overhead in a random access procedure and a TA maintenance procedure and waste system resources.